1. Field of the Invention:
This invention relates to an acrylic resin-pre-coated metal having excellent workability at room temperature. This invention further relates to an acrylic resin coating layer having minimum strain and high surface hardness resulting from heat treatment subsequent to working of the metal.
2. Description of the Prior Art:
Hitherto, pre-coated metal sheets have found wide use in industry. Pre-coated metal sheets have been prepared by surface coating steel, zinc-plated steel, aluminum and the like either in coil or cut-sheet form with a coating material or laminated with a synthetic resin flim. After the coating process, the metal sheets have been subjected to plastic working, such as press forming, with the aforesaid coated or laminated surfaces being left intact. The sheets require no further coating for protection or decoration of the surfaces of the metal sheets. Recently, pre-coated metal sheets have found wide use in the sheet-forming industry, because of their attractive advantages, such as elimination of a coating step which saves manpower.
Known pre-coated metal sheets may be generally classified into two types: those having a hardened or set layer composed of a thermosetting acrylic resin and those having a plasticized resin-coated layer composed of soft polyvinyl chloride. The former type has the advantage that the surface is extremely hard and resistant to scratches, but suffers from the disadvantage of brittleness and poor workability. On the other hand, the latter type has the advantage of satisfactory workability to the same degree as that of the base metal sheet, but suffers from the disadvantage of scratching. Additional disadvantages experienced with both types of pre-coated metal sheets include residual working strain in the resin-coated layers, low resistance to chemicals and poor weatherability. In other words, conventional pre-coated metal sheets fail to provide sufficient workability for satisfactory tight or contact-bending, sufficient hardness of at least as high as 4 H pencil core hardness and sufficient residual working strain in the resin-coated surfaces of the final products.
A need exists therefore for a pre-coated metal sheet which will overcome the above disadvantages of prior art sheets.